1. Identifying temporal patterns and controlling factors in methane ebullition at Sallie’s Fen, a temperate peatland site, using automated chambers Jordan Goodrich Advisors: Ruth Varner, Steve Frolking, Bryan Duncan

2. Motivation  Recent return to high growth rate in the atmospheric burden points to northern wetlands as contributor [Dlugokencky et al. 2009]  Thawing permafrost may release large stores of carbon by enhancing CH 4 emissions [e.g. Christensen et al. 2004]  Identify local processes and mechanisms to help constrain global trends Abisko, Sweden: CAMEL Project

3. Wetland CH 4  Anaerobic microbial production at depth creates a gradient with the overlying atmosphere  Subsequent transport upward can occur via three pathways: diffusion, plant mediated transport and ebullition (bubbling)  Bubbles form when pCH 4 (aq) exceeds hydrostatic pressure  shown to contain up to 70% CH 4  release has been related to falling atmospheric pressure and threshold peat bubble content

4. Objectives  Use automated chambers to measure CH 4 flux and quantify ebullition magnitude and frequency  Characterize the controls on CH 4 ebullition at various timescales (seasonal, synoptic, diel)  Estimate the proportion of total CH 4 flux contributed by ebullition at Sallie’s Fen

5. Site & Methods  Sallie’s Fen is located in Southeast NH, USA (43º12.5’N, 71º3.5’W) - peat depth 2.0-4.5 m, basal date ~9500yrs  Ten automated chambers close at random for either six or ten minutes at a time  Chamber head space concentration over time is measured with a cavity ring-down spectroscopy analyzer (one measurement every 2 sec)

7. * Flux from this curve: 185.2 mgCH 4 m -2 day -1

10. Ebullition Frequency

11. Water Table Effect  Reduction in pressure on CH 4 stored at depth [Windsor et al. 1992]  Easier to transport through air than water - increased diffusivity [ Moore and Roulet, 1993 ]  No clear relationship with atmospheric pressure - unlike previous studies - e.g. Tokida et al. 2005, Tokida et al. 2007, Waddington et al. 2009

12. Cumulative Summary: Jun-Aug 2009 Episodic ebullition as percent of total: 2 - 12%

13. Conclusions  Peat hydrology exhibits a strong control on CH 4 ebullition on synoptic timescales  Episodic ebullition can contribute a significant portion of the total CH 4 released during summer months at Sallie’s Fen, but our estimate is smaller than other field chamber studies  Modeling implications  Will the proportion of total flux contributed by ebullition increase or decrease in a changing climate?  In permafrost regions, will this pathway lead to significant release from carbon stored at depth?

14. Acknowledgements M.S. committee: Ruth Varner, Steve Frolking, Bryan Duncan Research & Discover Program (NASA & UNH) Michael Keller (Instrument) & Jack Dibb, Sallie Whitlow and Nicola Blake (Sallie’s Fen) Rob Braswell, Jill Bubier, Patrick Crill, Tom Milliman, Tuula Larmola Fellow students - Haley W., Claire T., Gennie N., Frankie S., Chelsea C., Eric K. Questions?

15. Ebullition Magnitude Distribution Arbitrary model units [Coulthard et al. 2009] Indicative of poorly decomposed peat with open poor structure (i.e. low bulk density)

16. Diel Pattern in Ebullition Frequency

17. Cumulative Summary - Summer only  Scale the daily frequency estimates  Based on area of each chamber  Based on amount of time the chamber was closed each day  Sample from the magnitude distribution  Take random samples as many times as indicated by the scaled frequency estimate for each day  Add them for each day to get a daily sum  Bootstrap the sampling to get uncertainty estimate (95% Confidence Intervals)

18. Uncertainty in Emission Estimates